This invention relates generally to test systems for measuring the performance of visual displays and, particularly, to a system having dual stages for providing five-axis motion for use in testing a visual display.
Present systems for testing visual displays, particularly flat panel displays, provide measurements concerning contrast ratio, luminance uniformity, chromaticity uniformity, viewing angle dependence, luminous efficiency and other such display characteristics. These measurements may be used, for example, by display manufacturers and researchers for gathering performance data, comparing the performance of materials, for new product evaluation and for quality control purposes. The Video Electronics Standards Association (VESA) publication "Flat Panel Display Measurements Standard (Proposal)," Doc. #136, Nov. 10, 1997, provides standard measurement procedures to quantify flat panel display characteristics.
Standard test procedures require the measurement of the display's light output at various locations and from various angles relative to the display surface. Positioning apparatus is available for moving a light measuring device, such as a photometer or colorimeter, relative to a stationary display under test or for moving the display relative to a stationary light measuring device. However, conventional positioning apparatus are not well suited for concurrently controlling both motions which results measurement inaccuracies. One disadvantage with conventional systems is that when examining a particular spot on the display, turning and tipping the display or the light measuring device moves the location of the spot within the light measuring device's field of view. Further, conventional display testing systems are not adaptable for use with a number of different light measuring devices nor do they provide automated testing to obtain a full range of normal and off-normal electro-optical performance measurements.